1. Field of Invention
The present invention relates to a quick coupler for coupling a tool like for example a scoop, shell grab or demolition tongs to a tool guide such as an excavator arm or the like, comprising a coupling receptacle for receiving a first locking part and a locking receptacle for receiving a second locking part, wherein to the coupling receptacle a securing element is associated for catching and/or securing the first locking part in the coupling receptacle and to the locking receptacle a locking element is associated for locking the second locking part in the locking receptacle, wherein the locking element and the securing element are actuable via a common pressure circuit having an unlocking pressure port and a locking pressure port selectively connectable with a pressure source or a return line via a valve means.
2. Background and Related Art
On construction machines such as hydraulic excavators or joint grabs such as wood handling machines or demolition equipment or similar material handling machines there are frequently used quick couplers for coupling various tools such as buckets, shell grabs or demolition tongs to an excavator arm or similar tool guides such as articulated arm booms, in order to be able to use various tools without long retooling times. As locking elements, such quick couplers in particular can include two spaced locking axles on one coupling part, whereas the other coupling part, in particular the excavator-arm-side coupling part, can include a preferably hook-shaped coupling receptacle for hooking into a first one of the two locking axles and a locking receptacle for locking at the second locking axle. After hooking the first locking axle into the coupling receptacle, the two coupling parts can be pivoted relative to each other, wherein the locking axle sitting in the coupling receptacle forms the axis of rotation, so that the second locking axle moves into the locking receptacle and/or is swiveled into the same, where the second locking axle then can be locked by a locking element such as for example an extendable wedge, so that at the same time it is no longer possible either to move the first locking axle out of the coupling receptacle. The locking axles on the one coupling part can be formed by locking bolts which on the corresponding coupling part can extend in particular parallel to each other, wherein instead of such bolts, however, other structural parts of the coupling part such as protruding noses, knuckles, engagement stubs in the form of protrusions or recesses for example in the form of pockets also can serve as locking part, which are adapted to the shape of the coupling receptacle or the locking receptacle of the other coupling part.
To prevent the first locking axle from again being released from the coupling receptacle during the swiveling operating after hooking the first locking axle into the coupling receptacle, it has been proposed already to associate a securing element for example in the form of a spring-tensioned snap-in wedge to the coupling receptacle, which on hooking the locking axle into the coupling receptacle catches the locking axle and secures the same in the coupling receptacle. When the locking axle moves into the coupling receptacle, the safety catch is pushed back, until the position completely hooked in is reached, so that the safety catch can again snap back and block the path of movement out of the coupling receptacle. To be able to also move the first locking axle out of the coupling receptacle and/or unhook the same when demounting a tool after unlocking the locking receptacle, this securing element must again be released and/or be moved into its clearing position. This can be effected with actuation by a pressure medium, for example by a single-acting pressure medium cylinder, which is able to move the securing element against its spring bias into the locking and/or blocking position and back into the clearing position. Climbing down of the machine operator and/or a manual operation thereby can be avoided.
To make the actual locking mechanism, which in operation is transmitting power and by which the second locking element for example in the form of a locking axle is fixed and/or locked in the locking receptacle, independent of the actuation of the securing element associated to the coupling receptacle, clearing and/or releasing the securing element at the coupling receptacle is usually accomplished by a separate pressure medium circuit, which is controllable independently of the pressure medium circuit for actuating the locking mechanism and/or is formed separate there from. This decoupling is performed to prevent that disturbances at the securing element can pass over to the actual locking mechanism and during operation can affect an unwanted release of the coupler lock. Such disturbances for example might be pressure losses at sealing elements, for example, which are provided in pressure circuit portions leading to the securing element of the coupling receptacle. Such quick coupler with separate pressure circuits decoupled from each other for actuating the locking mechanism and for unlocking the securing element at the coupling receptacle are shown for example in the document EP 1852555 A2.
Since in practice in the past frequently sold quick couplers of the type, which still are in use, have not been provided with such additional securing element at the coupling receptacle, it would be desirable to not only provide such additional lock at the coupling receptacle of new appliances, i.e. new quick couplers, but also to be able to retrofit the same at old quick couplers. The solution shown in the document EP 1852555 A2 is also suitable in principle for retrofitting already existing quick couplers, but due to the separate pressure circuit for actuating the securing element of the coupling receptacle it requires three hydraulic ports, namely two ports for actuating the actual locking mechanism and a further pressure port for unlocking the securing element of the coupling receptacle. However, only two hydraulic pressure ports frequently are present on existing appliances, so that retrofitting with such additional lock at the coupling receptacle often is not possible.
In order to provide for an easy-to-actuate additional lock with only one pressure medium circuit and a limited number of pressure medium ports, DE 20 2012 007 124 suggests to connect the additional securing element to the pressure circuit via a pressure switching valve which pressure circuit has in principle been provided for actuating the main locking element. The pressure circuit thereby can be raised to a higher pressure level by avoiding and/or bypassing a pressure reducing valve, at which higher pressure level the pressure switching valve opens so that the additional lock can be released in the direction opposite to its spring pre-load.
Such connection of the additional lock to the pressure circuit of the main lock has so far, however, been unsatisfactory in so far as locking of the additional lock is effected only by means of spring pre-tension so that in the case of wear of the spring device it might occur that, upon opening of the additional lock, the adjust cylinder filled with hydraulic oil cannot be moved back safely and fast enough and the additional lock cannot be locked again. In addition, the hybrid construction method of actuators provided for so far, which provides for a hydraulic opening and a mechanical pretensioned closing of the additional lock, is relatively complex and intricate.
Proceeding there from, it is the object underlying the present invention to create an improved quick coupler of the type mentioned above, which avoids the disadvantages of the prior art and develops the latter in an advantageous way. In particular, there should be created an easily structured, permanently safely actuable additional lock at the coupling receptacle, which does not require an increased number of pressure medium ports.